Light with an energy flux of `18W//cm^(2)` falls on a non-reflecting surface at normal incidence. The pressure exerted on the surface is

Options

A. `2N//m^(2)`
B. `2xx10^(-4)N//m^(2)`
C. `6N//m^(2)`
D. `6xx10^(-4)N//m^(2)`

Answer

D

Explanation

Radiation pressure `P_("red")` due to light falling on a non-reflecting surface at normal incidence is given by
`P_("rad")=("Energy flux")/("Speed of light")=("18 W/cm"^(2))/(3xx10^(8)m//s)`
`=(18xx10^(4)W//m^(2))/(3xx10^(8)m//s)=6xx10^(-4)N/m^(2)`